Bisphosphonate-related osteonecrosis: genetic and acquired risk factors

Efficacy of hyaluronic acid, absorbable collagen sponge, and their combination in minimizing bisphosphonate-related osteonecrosis of the jaws (BRONJ) after dental extraction: a preliminary animal histomorphometric study

Introduction

There is no study on the effectiveness of hyaluronic acid (HA) placement either with or without absorbable collagen sponge (ACS) in reducing or preventing bisphosphonate-related osteonecrosis of the jaws (BRONJ). This preliminary animal study examined the efficacy of this clinically important treatment.

Methods

For simulating BRONJ, zoledronic acid was administered to 40 rats for 5 weeks. Two weeks later, a right first molar was extracted from each rat. The rats were randomized into four groups of socket treatments: control (empty extraction socket) or with sockets filled with ACS, HA, or HA+ACS (n=4×10). After 2 weeks, 5 rats in each group were sacrificed and subjected to histopathologic and histomorphometric evaluation. Eight weeks post-surgically, the rest of rats were euthanized and histologically examined. The Kruskal-Wallis test was used to compare the four treatments at each time point (α=0.05).

Results

Six rats were lost overall. In the second week, vascularization was higher in ACS group (P<0.05); osteoclast activity was not different between groups (P>0.05); empty lacunae were the most and fewest in control and HA+ACS groups, respectively (P<0.05); eosinophil infiltration was maximum in HA group (P<0.05); lymphocyte counts were maximum and minimum in the HA+ACS and ACS groups, respectively (P<0.05); the highest and lowest neutrophil counts were seen in ACS and control groups, respectively (P<0.05); and the extent of live bone did not differ between groups (P>0.05). In the eighth week, vascularization was not different in groups (P>0.05); the highest and lowest osteoclast activities were seen in the control and HA+ACS groups, respectively (P<0.05); empty lacunae were the most and fewest in control and HA+ACS, respectively (P<0.05); maximum and minimum numbers of eosinophils were in control and HA+ACS groups, respectively (P<0.05); HA and control groups exhibited the highest and lowest lymphocyte counts, respectively (P<0.05); the lowest and highest neutrophil counts were observed in HA+ACs and control groups, respectively (P<0.05); and the highest and lowest extents of the live bone were observed in HA+ACS and control groups, respectively (P<0.05).

Conclusions

Within the limitations of this preliminary animal study, HA and especially HA+ACS seem a proper method for preventing or treating BRONJ.

Treatment of Stage 2 Medication-Induced Osteonecrosis of the Jaw: A Case Series

Medication-induced jaw osteonecrosis (MRONJ) is a rare and serious disease with a negative impact on patients’ quality of life, whose exact cause remains unclear and which may have a multifactorial origin. Although there are different therapeutic protocols, there is still no consensus. This case series evaluated three patients diagnosed with staged 2 MRONJ treated at the University of Murcia dental clinic according to the protocols described by the Spanish Society of Oral and Maxillofacial Surgery and the American Association of Oral and Maxillofacial Surgeons. Within 12 months of the application of therapeutic protocols, the lesions were completely healed in all cases. Radiography showed slow but progressive healing with normal bone structure. Conservative treatment with antibiotics, chlorhexidine rinses and minimally invasive surgical intervention with necrotic bone resection is effective in treating stage 2 of MRONJ. In cases of refractory osteonecrosis, the application of platelet and leukocyte-rich fibrin (PRF-L) in the surgical approach improves the outcome in soft tissue healing and bone regeneration but further research is needed to confirm its effectiveness.

Extensive protein expression changes induced by pamidronate in RAW 264.7 cells as determined by IP-HPLC

Background

Bisphosphonate therapy has become a popular treatment for osteoporosis, Paget’s disease, multiple myeloma, osteogenesis imperfecta, myocardial infarction, and cancer despite its serious side effects. Bisphosphonate-induced molecular signaling changes in cells are still not clearly elucidated.

Methods

As bisphosphonates are primarily engulfed by macrophages, we treated RAW 264.7 cells (a murine macrophage cell line) with pamidronate and investigated global protein expressional changes in cells by immunoprecipitation high performance liquid chromatography (IP-HPLC) using 218 antisera.

Results

Pamidronate upregulated proliferation-activating proteins associated with p53/Rb/E2F and Wnt/β-catenin pathways, but downregulated the downstream of RAS signaling, pAKT1/2/3, ERK-1, and p-ERK-1, and subsequently suppressed cMyc/MAX/MAD network. However, in situ proliferation index of pamidronate-treated RAW264.7 cells was slightly increased by 3.2% vs. non-treated controls. Pamidronate-treated cells showed increase in the expressions of histone- and DNA methylation-related proteins but decrease of protein translation-related proteins. NFkB signaling was also suppressed as indicated by the down-regulations of p38 and p-p38 and the up-regulation of mTOR, while the protein expressions related to cellular protection, HSP-70, NRF2, JNK-1, and LC3 were upregulated. Consequently, pamidronate downregulated the protein expressions related to immediate inflammation,cellular differentiation, survival, angiogenesis, and osteoclastogenesis, but upregulated PARP-1 and FAS-mediated apoptosis proteins. These observations suggest pamidronate affects global protein expressions in RAW 264.7 cells by stimulating cellular proliferation, protection, and apoptosis but suppressing immediate inflammation, differentiation, osteoclastogenesis, and angiogenesis. Accordingly, pamidronate appears to affect macrophages in several ways eliciting not only its therapeutic effects but also atypical epigenetic modification, protein translation, RAS and NFkB signalings. Therefore, our observations suggest pamidronate-induced protein expressions are dynamic, and the affected proteins should be monitored by IP-HPLC to achieve the therapeutic goals during treatment.

Zoledronate Enhances Osteocyte-Mediated Osteoclast Differentiation by IL-6/RANKL Axis

Bisphosphonates are one of the most widely used synthetic pyrophosphate analogues for the treatment of bone resorbing diseases such as osteoporosis, multiple myeloma, and bone metastases. Although the therapeutic usefulness of bisphosphonates mainly depends on their anti-osteoclastogenic effect, a severe side-effect of bisphosphonates called bisphosphonate-related osteonecrosis of the jaw (BRONJ) could not be explained by the anti-osteoclastogenic effect of bisphosphonates. In the present study, we have evaluated the changes in osteoclastogenesis- or osteoblastogenesis-supporting activities of osteocytes induced by bisphosphonates. Zoledronate, a nitrogen-containing bisphosphonate, markedly increased both the receptor activator of nuclear factor kB ligand (RANKL) as well as sclerostin in osteocyte-like MLO-Y4 cells, which were functionally revalidated by osteoclast/osteoblast generating activities of the conditioned medium obtained from zoledronate-treated MLO-Y4 cells. Of note, the zoledronate treatment-induced upregulation of the RANKL expression was mediated by autocrine interleukin-6 (IL-6) and subsequent activation of the signal transducer and activator of transcription 3 (STAT3) pathway. These results were evidenced by the blunted RANKL expression in the presence of a Janus activated kinase (JAK2)/STAT3 inhibitor, AG490. Also, the osteoclastogenesis-supporting activity was significantly decreased in zoledronate-treated MLO-Y4 cells in the presence of IL-6 neutralizing IgG compared to that of the control IgG. Thus, our results show previously unanticipated effects of anti-bone resorptive bisphosphonate and suggest a potential clinical importance of osteocytes in BRONJ development.

Viewpoints of dentists on the use of bisphosphonates in rheumatology patients

OBJECTIVES

Alhough typically prescribed in oncology, bisphosphonates (BPs) are also employed in rheumatology, particularly for the treatment of osteoporosis, sometimes resulting in complications, such as osteonecrosis of the jaw. Because of different opinions between rheumatologists and dentists on BP use, this study aimed to assess the views of dentists regarding administration of BPs in rheumatology.

METHODS

A questionnaire was sent to 880 dentists from the Auvergne region of France to determine their views on BP treatment.

RESULTS

We obtained 382 (43.4%) responses and analysed 376 (58.7% men). In total, 156 (41.5%) of the responders analysed had attended an in-service training course (ISTC) on the topic. A total of 237 (63.0%) systematically inquired as to whether their patients were undergoing BP treatment; this proportion was higher among those who had been practicing for fewer than 10 years (P < 0.004). For patients receiving BPs, 84.5% of practitioners felt ill at ease about performing dental surgery (n = 318) and 11% felt ill at ease about performing nonsurgical dental care (n = 41); 67% stated that their practice differed depending on the method of BP administration (per os or intravenously). Overall, 53.7% of practitioners felt uncomfortable when asked by a rheumatologist whether a given patient's dental status permitted prescription of BP (n = 202). This proportion was higher among those who had never attended an ISTC (62.6% vs. 50.7%; P < 0.03).

CONCLUSIONS

Dentists feel ill at ease providing dental surgery to patients receiving BPs. Closer collaboration and better information-sharing between rheumatologists and dentists is necessary to facilitate the administration of BPs in rheumatology.

Extensive Surgical Procedures Result in Better Treatment Outcomes for Bisphosphonate-Related Osteonecrosis of the Jaw in Patients With Osteoporosis

PURPOSE

To identify the risk factors associated with relapse or treatment failure after surgery for bisphosphonate-related osteonecrosis of the jaw (BRONJ) in patients with osteoporosis.

PATIENTS AND METHODS

We performed a retrospective cohort study of BRONJ in patients with osteoporosis who had undergone surgical procedures from 2004 to 2016 at the Department of Oral and Maxillofacial Surgery, Seoul National University Dental Hospital. The predictor variables were a set of heterogeneous variables, including demographic (age, gender), anatomic (maxilla or mandible, or both, affected location), clinical (disease stage, etiology, comorbidities, history of intravenous bisphosphonate intake), time (conservative treatment before surgery, bisphosphonate treatment before the development of BRONJ, discontinuation of the drug before surgery, interval to final follow-up, interval to reoperation in the case of relapse or treatment failure), and perioperative variables (type of anesthesia, type of surgical procedures). The primary outcome variable was relapse after surgery that required reoperation (yes vs no). The descriptive and bivariate statistics were computed to assess the relationships between the study variables and the outcome. To determine the risk factors, we conducted a survival analysis using the Cox model.

RESULTS

The final sample included 325 subjects with a median age of 75 years, and 97% were women. After surgery, 30% of patients did not completely recuperate and underwent repeat surgery. The interval from the first surgery to reoperation ranged from 10 days to 5.6 years. Relapse or treatment failure most often occurred immediately after surgery. The type of surgical procedure and mode of anesthesia were the most important factors in the treatment outcome. A drug holiday did not appear to influence the likelihood of relapse after surgery.

CONCLUSIONS

Treatment of BRONJ in patients with osteoporosis might benefit from more careful and extensive surgical procedures rather than curettage performed with the patient under local anesthesia.

Epidemiological study of alendronate-related osteonecrosis of the jaw in the southeast of Scotland

We aimed to establish the incidence of alendronate-related osteonecrosis of the jaw (ONJ) in the southeast of Scotland, and to assess the effect of corticosteroids on it. We studied a prospective case series of patients between June 2004 and March 2012 separated into steroid and non-steroid groups. There were 34 cases of alendronate-related ONJ and 78732 drug patient years (DPY) of alendronate, making the overall occurrence 43.1 cases/100000 DPY. There were 12 patients in the steroid group (mean (range) age 68.2 (48-87) years) making 42.5 cases/100000 DPY, and 22 in the non-steroid group (mean (range) age 76.2 (63-91) years) making 119.6 cases/100000 DPY. The mean (range) age at presentation of alendronate-related ONJ was significantly lower in the steroid group (68.2 (48-87) compared with 76.2 (63-91) years, p=0.019) as was the duration of exposure to alendronate before it developed (28.9 (6-120) compared with 61.3 (13-168) months, p=0.03). The overall incidence seems to be higher in the southeast of Scotland than elsewhere. Concurrent use of corticosteroids is not associated with an increased incidence of alendronate-related ONJ, but it seems to reduce the duration of exposure before it develops. Age is likely to be a confounding factor.

Bisphosphonate-related osteonecrosis of the jaw: awareness and level of knowledge of Lebanese physicians

PURPOSE

Bisphosphonate-induced osteonecrosis of the jaw (ONJ) is a potentially destructive complication, particularly encountered in oncology. It is supposed that awareness and good knowledge of this disease by physicians are important factors of its early detection and management. This study aims to evaluate the level of knowledge among a sample of Lebanese physicians with regard to this complication.

METHODS

An observational cross-sectional study was conducted at Hôtel-Dieu de France hospital between March and June 2013. Data were collected through a self-administered questionnaire distributed to 190 eligible physicians in the departments involved in prescribing bisphosphonates and managing the ONJ.

RESULTS

A total of 136 valid responses were obtained (response rate 71.6 %). Eighty-six (63.2 %) physicians were treating patients with bisphosphonates: the most prescribed form being the weekly oral bisphosphonates for osteoporosis followed by zoledronate several times yearly for bone malignancies. Fifty-one (37.5 %) participants were unaware of bisphosphonate-related ONJ. Furthermore, the level of knowledge was relatively poor: the mean score of all participants was 12.42 ± 10.08, while 77 (56.6 %) had a global score more than 16 over 30. There were statistically significant associations between the level of knowledge and physicians' specialty (p value <0.0001), whether or not they prescribe bisphosphonates (p value = 0.039), the most frequently form prescribed (p value = 0.048), whether or not they attend patients already on bisphosphonate (p value = 0.047), whether or not they have observed (p value = 0.004) and treated (p value = 0.002) exposed necrotic bone of the jaw.

CONCLUSIONS

Our study revealed a deficient knowledge regarding bisphosphonate-related ONJ among Lebanese physicians. Appropriate training strategies to increase their awareness are required.

Autologous platelet concentrates for bisphosphonate-related osteonecrosis of the jaw treatment and prevention. A systematic review of the literature

PURPOSE

Bisphosphonate related osteonecrosis of the jaw (BRONJ) is an adverse drug reaction consisting of progressive bone destruction in the maxillofacial region of patients under current or previous treatment with a bisphosphonate. Autologous platelet concentrates (APC) demonstrated to enhance bone and soft tissue healing in oral surgery procedures. The present systematic review aimed at evaluating if APC may improve treatment and prevention of BRONJ in patients under bisphosphonate therapy.

METHODS

MEDLINE, Scopus and Cochrane databases were searched using terms like bisphosphonates, osteonecrosis, BRONJ, platelet concentrate, PRP, PRF, PRGF. No language, publication date and study design limitation was set. A hand search of the bibliographies of identified articles was also performed. The primary outcome was recurrence/onset of BRONJ after oral surgery procedures.

RESULTS

Eighteen studies were included, reporting on 362 patients undergoing oral surgery in combination with APC. The adjunct of APC in BRONJ treatment significantly reduced osteonecrosis recurrence with respect to control. APC was associated with a lower BRONJ incidence after tooth extraction, though not significant. Heterogeneity was found regarding bisphosphonate type, clinical indication, treatment duration, triggering factors, study design, follow-up duration, type of APC, outcomes adopted to evaluate treatment success.

CONCLUSION

Though the results of this review must be cautiously interpreted, due to the low evidence level of the studies included, and the limited sample size, they are suggestive of possible benefits of APC when associated with surgical procedures for treatment or prevention of BRONJ. To confirm such indication, prospective comparative studies with a large sample size are urgently needed.

Does an alkaline environment prevent the development of bisphosphonate-related osteonecrosis of the jaw? An experimental study in rats

OBJECTIVE

To investigate the preventive effect of locally applied sodium bicarbonate on bisphosphonate-related osteonecrosis of the jaw (BRONJ).

STUDY DESIGN

Thirty-six Sprague-Dawley rats were divided into 4 groups. Animals in group I received 0.1 mg/kg sterile saline 3 times per week for 8 weeks. Groups II, III, and IV received intraperitoneal zoledronate injection in the same manner with the same frequency and duration. The right first molar tooth was extracted in groups III and IV. One mL 8.4% sodium bicarbonate (SB) was applied to the extraction socket at the time of extraction in group IV. The effect of locally applied SB as an alkalizing agent was evaluated by histomorphometric analysis.

RESULTS

BRONJ was observed in none of the animals in the control groups, 67% of the animals in the tooth extraction group, and none of the animals in the local SB application group (P < .01).

CONCLUSIONS

Administration of locally applied SB had positive effects on the prevention of BRONJ in animals, but further studies are required to verify the effectiveness of this form of treatment before its use in humans.

Bisphosphonates induce the osteogenic gene expression in co-cultured human endothelial and mesenchymal stem cells

Bisphosphonates (BPs) are known to affect bone homeostasis and also to have anti-angiogenic properties. Because of the intimate relationship between angiogenesis and osteogenesis, this study analysed the effects of Alendronate (AL) and Zoledronate (ZL) in the expression of endothelial and osteogenic genes on interacting endothelial and mesenchymal stem cells, an issue that was not previously addressed. Alendronate and ZL, 10(-12) -10(-6) M, were evaluated in a direct co-culture system of human dermal microvascular endothelial cells (HDMEC) and human bone marrow mesenchymal stem cells (HMSC), over a period of 14 days. Experiments with the respective monocultures were run in parallel. Alendronate and ZL caused an initial dose-dependent stimulation in the cell proliferation in the monocultures and co-cultures, and did not interfere with their cellular organization. In HDMEC monocultures, the expression of the endothelial genes CD31, VE-cadherin and VEGFR2 was down-regulated by AL and ZL. In HMSC monocultures, the BPs inhibited VEGF expression, but up-regulated the expression of the osteogenic genes alkaline phosphatase (ALP), bone morphogenic protein-2 (BMP-2) and osteocalcin (OC) and, to a greater extent, osteoprotegerin (OPG), a negative regulator of the osteoclastic differentiation, and increased ALP activity. In co-cultured HDMEC/HMSC, AL and ZL decreased the expression of endothelial genes but elicited an earlier and sustained overexpression of ALP, BMP-2, OC and OPG, compared with the monocultured cells; they also induced ALP activity. This study showed for the first time that AL and ZL greatly induced the osteogenic gene expression on interacting endothelial and mesenchymal stem cells.

Interleukin-6 concentration changes in plasma and saliva in bisphosphonate-related osteonecrosis of the jaws

AIM

To determine the plasma and saliva levels of IL-6 in patients with bisphosphonate-related osteonecrosis of the jaws (BRONJ) and to investigate whether there is a correlation between more advanced stages of BRONJ and levels of IL-6.

MATERIAL AND METHODS

We studied three groups: group 1 consisted of 30 patients with BRONJ due to intravenous bisphosphonates (ivBP), group 2 consisted of 25 patients treated with ivBP but without BRONJ, and group 3 consisted of 15 healthy controls. In each case, we assayed plasma and saliva IL-6 samples using an ELISA test.

RESULTS

Significantly, higher IL-6 values were found in both saliva and plasma in group 1 vs groups 2 and 3 (P < 0.01). Group 1 showed no differences in plasma or saliva IL-6 according to patient gender (P > 0.05), type of tumor, BRONJ location, etiology of BRONJ, or disease stage (P > 0.05). We found higher plasma and saliva IL-6 values in the more advances stages of BRONJ, although the differences were not statistically significant.

CONCLUSIONS

Plasma and saliva IL-6 values were higher in our patients with BRONJ than in controls and therefore might be a useful tool for monitoring the severity of BRONJ.

Pharmacogenetics of osteoporosis: towards novel theranostics for personalized medicine?

Osteoporosis is a complex multifactorial bone disorder with a strong genetic basis. It is the most common, severe, progressive skeletal illness that has been increasing, particularly in developed countries. Osteoporosis will no doubt constitute a serious clinical burden in healthcare management in the coming decades. The genetics of osteoporosis should be analyzed from both the disease susceptibility and the pharmacogenetic treatment perspectives. The former has been widely studied and discussed, while the latter still requires much more information and research. This article provides a synthesis of the literature on the genetics of osteoporosis and an update on progress made in pharmacogenetics of osteoporosis in recent years, specifically regarding the new molecular targets for antiresorptive drugs. In-depth translation of osteoporosis pharmacogenetics approaches to clinical practice demands a new vision grounded on the concept of "theranostics," that is, the integration of diagnostics for both disease susceptibility testing, as well as for prediction of health intervention outcomes. In essence, theranostics signals a broadening in the scope of inquiry in diagnostics medicine. The upcoming wave of theranostics medicine also suggests more distributed forms of science and knowledge production, both by experts and end-users of scientific products. Both the diagnosis and personalized treatment of osteoporosis could conceivably benefit from the emerging postgenomics field of theranostics.

The effects of chronic zoledronate usage on the jaw and long bones evaluated using RANKL and osteoprotegerin levels in an animal model

The discovery of the receptor activator of nuclear factor kappaB (RANK), RANK ligand (RANKL), and osteoprotegerin (OPG) system (RANK/RANKL/OPG system) has been one of the most important advances in bone biology in the last decade. We investigated how the chronic application of bisphosphonate affects the RANKL and OPG levels in an animal model and whether this effect may be related to bisphosphonate-related osteonecrosis of the jaws (BRONJ). Thirty female Sprague-Dawley rats were used in this study. The rats were randomly divided into three groups (10 in each): Z, the zolendronate group, injected with zolendronate for 10 weeks; S, a control group, injected with saline solution for 10 weeks; and C, a control group, in which no injection was given. RANKL values in the tibia were increased in the Z group when compared with the two controls; however, the RANKL values in the mandible were decreased when compared with the controls. Although the differences did not reach statistical significance, the mandibular OPG values were increased in the Z group when compared with the C and S groups. The mechanism of RANKL negation and absence in osteoclastic activation could be a predisposing factor for the development of BRONJ.

Assessing the risk of osteonecrosis of the jaw due to bisphosphonate therapy in the secondary prevention of osteoporotic fractures

SUMMARY

There is evidence that the use oral bisphosphonates can lead to osteronecrosis of the jaws (ONJ). Although the occurrence of ONJ appears rare among oral bisphosphonates (BPs) users, it is important to know that it exists and can be opportunely minimized.

INTRODUCTION

The purpose of this study is to evaluate the association between BPs prescribed for the secondary prevention of osteoporotic fractures and the occurrence of ONJ.

METHODS

An Italian record linkage claims database with a target population of around 18 million individuals (6 million over 55 years of age) constituted the data source. We conducted a nested case-control study within a cohort of individuals aged 55+ years old, who were discharged from hospitals with a primary diagnosis of incident osteoporotic fracture. The date related to the discharge diagnosis of ONJ was the index date. Conditional logistic regression for matched data was fitted to estimate the odds ratio (OR) along with 95 % confidence intervals (95 % CI) for the likely association between use of BPs and the risk of ONJ.

RESULTS

Any one of the 61 ascertained cases of ONJ (incidence rate, 36.6 per 100,000 person-years) was matched to 20 controls for a total of 1120 controls. When the exposure to BPs was modeled according to recency (i.e., exposure time window prior to the index date) of use, the adjusted OR (95 % CI) for current users was 2.8 (1.3-5.9) against never users. The cumulative use of BPs has shown to increase the incidence of ONJ among patients with primary osteoporotic fractures, although not statistically significant risk has been observed.

CONCLUSIONS

Although the risk of BP-related ONJ appears low in non-oncological indications, it is important to be aware that it exists and to know how it may be predicted and possibly minimized.

[Bisphosphonate related osteonecrosis of the jaw and infection with Actinomyces]

BACKGROUND AND OBJECTIVE

Bisphosphonate related osteonecrosis of the jaw (BRONJ) has raised considerable interest since its recent description. Its pathogenesis is not yet clarified; formerly it has been considered a non-infectious complication, but recent studies seem to implicate bacteria of the genus Actinomyces. The objective of this study is to analyze the cases of BRONJ in our institution.

PATIENTS AND METHODS

Review of medical records of patients diagnosed of BRONJ in the Maxillofacial Surgery Unit of our hospital.

RESULTS

We have found 11 cases of BRONJ in our hospital: 4 women taking oral alendronate or risendronate for osteoporosis and 7 cancer patients treated with intravenous zolendronic acid. All of them showed bone invasion by bacteria of the genus Actinomyces. Nine patients underwent prolonged treatment with amoxicillin with favourable clinical outcome in all of them, but 3 died of their malignancy. By contrast, one patient with beta-lactamic allergy and irregular treatment with erythromycin and tetracycline had a chronic evolution of the lesions. There was no information for other patient.

CONCLUSIONS

Actinomyces play an important role in the development of BRONJ and specific antibiotic treatment improves the prognosis of this process.

Bisphosphonate induced osteonecrosis of jaw in breast cancer patients: A systematic review

BACKGROUND

Bisphosphonate therapy is widely used for the treatment of bone metastasis in breast cancer patients.

AIM

The aim of this study is to estimate the overall prevalence of bisphosphonate induced osteonecrosis of jaw (BONJ) in breast cancer patients with bone metastasis.

MATERIALS AND METHODS

A literature review was conducted to search and evaluate all the articles that contained original data on the prevalence of BONJ in breast cancer patients from the year 2003-2009. Pubmed search terms used were bisphosphonate, osteonecrosis, breast cancer and jaw. Eleven publications that fulfilled the inclusion criteria were chosen for the study. Case reports and reviews were excluded from the analysis based on assessing the title and abstract.

RESULTS

Of the 2490 breast cancer patients, 69 developed BONJ with the overall prevalence rate of 2.8%. All the patients with BONJ had received zoledronate or pamidronate, either alone or in combinations.

CONCLUSION

BONJ is a significant complication occurring in 2.8% of the breast cancer patients receiving bisphosphonates for metastatic bone disease. It is very important to identify the trigger factors associated with BONJ and also to establish guidelines for the prevention and effective treatment of this condition.

Non-exposed bisphosphonate-related osteonecrosis of the jaw: a critical assessment of current definition, staging, and treatment guidelines

Non-exposed bisphosphonate-related osteonecrosis of the jaw (BRONJ) is a newly reported complication arising from bisphosphonate therapy that presents with atypical symptoms and no apparent mucosal fenestration or exposure of necrotic bone. The clinical observation of the presence of necrotic bone underneath normal epithelial coverage was not conclusive for the diagnosis of BRONJ based on current guidelines established by the American Association of Oral and Maxillofacial Surgeons (AAOMS) and the American Society for Bone and Mineral Research (ASBMR), which specify the presence of clinically exposed necrotic bone for more than 8 weeks. Hence, the purpose of this review is to critically assess the current guidelines for diagnosis and management of BRONJ and propose a modified staging system and treatment guidelines to properly address the non-exposed variant of BRONJ lesions.

Is oral bisphosphonate-related osteonecrosis of the jaw an endemic condition?

Since the introduction of bisphosphonates to treat diseases that affect bone remodelling, there has been an increasing number of cases of bisphosphonate (BP)-related osteonecrosis of the jaw (BRONJ). Epidemiological data regarding BRONJ vary widely between studies, and a number of potential methodological biases have been detected. In some small preliminary studies, single nucleotide polymorphisms associated with an increased risk of BRONJ among cancer patients have been identified. However, genetic susceptibility to oral BP-related BRONJ has not previously been discussed. We suggest that epidemiological variability could be related to the existence of a susceptibility factor particularly prevalent in the population of a well-defined geographical region. To support our hypothesis we performed a search for published case series, only including those with at least 10 patients detected in a single city or a delimited geographical region; this showed that 55% of reports came from Mediterranean countries such as Italy, Israel, Spain and France. The finding does not appear to be conditioned by publication bias. Furthermore, conditions such as classic Kaposi sarcoma and beta-thalassaemia, though not exclusive to the Mediterranean region, also have a high prevalence in that area. We speculate that some of the patients included in the selected US and Australian series may be of Spanish or Italian descent. With an ageing population, the prevalence of osteoporosis will increase, and the number of cases of oral BP-related BRONJ may rise exponentially. Identification of risk groups with susceptibility to BRONJ will arise caution when prescribing BPs and will allow new preventive and therapeutic strategies to be developed.

The role of bisphosphonates in multiple myeloma: mechanisms, side effects, and the future

Zoledronic acid and pamidronate are two potent anticatabolic nitrogen-containing bisphosphonates (BPs) used extensively in diseases with high bone turnover such as multiple myeloma (MM). In this review we focus on their biology and their current and future use in MM, and highlight some of the most common and emerging side effects. Although the primary target cells for BPs are osteoclasts, new insights suggest other cell types of the bone microenvironment as possible targets, including osteoblasts, endothelial cells, immune cells, and cancer cells. Here, we focus on the current guidelines for the use of BPs in MM and address side effects such as renal toxicity, osteonecrosis of the jaw, and low-energy fractures. Finally, we approach the future of BP use in MM in the context of other bone-targeted agents, evaluating ongoing clinical trials addressing alternate dosing and schedules of BP administration in MM patients.

[Relationship between osteonecrosis of the jaw and bisphosphonate treatment]

Bisphosphonate treatment and its aetiopathogenic association with aseptic osteonecrosis of the jaw is one of the more prominent public health issues today. The aim of this review is to see into the mechanisms of bisphosphonate effects on bones described in literature (anti-osteoclastic activity, cytotoxicity, antiangiogenesis, genetic factors, and imbalance between osteoclasts and osteoblasts). Bisphosphonate treatment is the dominant cause of jaw necrosis. Epidemiological data show an exclusive incidence of osteonecrosis of the jaw in patients who took one or a combination of nitrogen-containing bisphosphonates. Risk factors vary by the bisphosphonate potency (particularly risky are the highly potent pamidronate and zoledronate, which are given intravenously), dosage, duration of treatment, and the illness. Jaw necrosis is most common in oncology patients, and only 5 % in patients with osteoporosis. From a dental-medical point of view, a good oral health is important because osteonecrosis often appears after a periodontal or oral surgical procedure.

Bisphosphonate-related osteonecrosis of the jaws: how to manage cancer patients

Bisphosphonate related osteonecrosis of the jaw (BRONJ) is defined as exposed necrotic bone appearing in the jaws of patients treated by systemic IV or oral BPs never irradiated in the head and neck area and that has persisted for more than 8 weeks. More than 90% of cases of osteonecrosis of the jaw have been in patients with cancer who received IV-BPs. The estimate of cumulative incidence of BRONJ in cancer patients with IV-BPs ranges from 0.8% to 18.6%. The pathogenesis of BRONJ appeared related to the potent osteoblast-inhibiting properties of BPs which act by blocking osteoclast recruitment, decreasing osteoclast activity and promoting osteoclast apoptosis. Dental extractions are the most potent local risk factor. Cancer patients wearing a denture could also be at increased risk of BRONJ. Non-healing mucosal breaches caused by dentures could be a portal for the oral flora to access bone, while the oral mucosa of patients on IV-BPs could also be defective. Whether periodontal disease is a risk factor for BRONJ remains controversial. Preventive measures are fundamental. Nevertheless, some teams have questioned its cost-effectiveness. The perceived limitations of surgical therapy of BRONJ led to the restriction of aggressive surgery to symptomatic patients with stage 3 BRONJ. The evidence-based literature on BRONJ is growing but there are still many controversial aspects.

The transcriptional regulation of the human CYP2C genes

In humans, four members of the CYP2C subfamily (CYP2C8, CYP2C9, CYP2C18, and CYP2C19) metabolize more than 20% of all therapeutic drugs as well as a number of endogenous compounds. The CYP2C enzymes are found predominantly in the liver, where they comprise approximately 20% of the total cytochrome P450. A variety of xenobiotics such as phenobarbital, rifampicin, and hyperforin have been shown to induce the transcriptional expression of CYP2C genes in primary human hepatocytes and to increase the metabolism of CYP2C substrates in vivo in man. This induction can result in drug-drug interactions, drug tolerance, and therapeutic failure. Several drug-activated nuclear receptors including CAR, PXR, VDR, and GR recognize drug responsive elements within the 5' flanking promoter region of CYP2C genes to mediate the transcriptional upregulation of these genes in response to xenobiotics and steroids. Other nuclear receptors and transcriptional factors including HNF4alpha, HNF3gamma, C/EBPalpha and more recently RORs, have been reported to regulate the constitutive expression of CYP2C genes in liver. The maximum transcriptional induction of CYP2C genes appears to be achieved through a coordinative cross-talk between drug responsive nuclear receptors, hepatic factors, and coactivators. The transcriptional regulatory mechanisms of the expression of CYP2C genes in extrahepatic tissues has received less study, but these may be altered by perturbations from pathological conditions such as ischemia as well as some of the receptors mentioned above.